2 digits in datagridview in column with possible NULL

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I fill the datagrid per code.
Setting the Format "N2" in Code or in Designer doesn´t make any difference.
The problem seems to be that I have NULL in this column too.
I want no display when NULL and and a 2-digit value when not NULL.
Is this possible?

Attempts with CDdec, Math.round don´t fit, because of error with NULL.

What I have tried:

dgvProduktion.Rows.Add(..., dreader("AZmin").ToString() ,...)

CDec and Math.round don´t work with NULL

Posted 16-Jun-23 0:19am

mitschkea

Updated 16-Jun-23 1:44am

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3 solutions

Solution 1

Add a null conditional operator: Member access and null-conditional operators and expressions: | Microsoft Learn[^]

C#

dgvProduktion.Rows.Add(..., dreader("AZmin")?.ToString() ,...)

Posted 16-Jun-23 0:25am

OriginalGriff

Comments

Graeme_Grant 16-Jun-23 6:29am

Not supported in VB ~~(I think)~~, you will get the following compile error:

BC30487	Operator '?' is not defined for type 'Double'

OriginalGriff 16-Jun-23 6:51am

You sure?
https://learn.microsoft.com/en-us/dotnet/visual-basic/language-reference/operators/null-conditional-operators

I just checked and it works for me:

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim str As String = Nothing
        If str?.ToString() Is Nothing Then
            Console.WriteLine("Yes")
        Else
            Console.WriteLine("No")
        End If
    End Sub

Graeme_Grant 16-Jun-23 6:58am

Hmm... .Net Core or .Net Framework. I used .Net Framework as many avoid .Net Core. Also, check my answer below.

His question indicates the value is numeric, not a string, hence the cast ToString. Try this test:

Dim value As Double = Nothing
Console.WriteLine(value?.ToString())

OriginalGriff 16-Jun-23 7:15am

If it's a Double, it can't contain a null value anyway - it's a value type, not reference.
It would have to be a Double? but that would mean he wouldn't get the problem anyway ... (I think, I've not played with nullable types in VB)

Graeme_Grant 16-Jun-23 7:16am

Nullable types have very limited support in VB. We are spoilt in C#, especially in .Net Core.

OriginalGriff 16-Jun-23 7:15am

Framework, WinForms.

Graeme_Grant 16-Jun-23 7:41am

Console .Net Framework 4.71 for me. Here is the full test app:

Module Module1

    Sub Main()

        Dim value As Double = Nothing

        'Fail with: BC30487	Operator '?' is not defined for type 'Double'
        Console.WriteLine(value?.ToString()) 

        Console.WriteLine(FormatData(value))

    End Sub

    Function FormatData(value As Double?) As String

        If value Is Nothing Then
            Return ""
        End If

        Return value.ToString()

    End Function

End Module

I could use:

Dim value As Double? = Nothing

however it is unclear what the OP is doing.

Solution 3

So it works:

Function FormatN2(value As String) As String
    If value = "" Then
        Return ""
    Else
        value = Math.Round(CDec(value), 2)
    End If

    Return value.ToString()
End Function

Posted 16-Jun-23 1:44am

mitschkea

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Graeme_Grant · Accepted Answer · 2023-06-16T00:29:00

Wrap the data in a method that handles the formatting.

For example, change:

C#

dreader("AZmin").ToString()

To:

C#

Function FormatData(value As Double?) As String

    If value Is Nothing Then
        Return ""
    End If

    Return value.ToString()

End Function

Where value_type is the filed value type, eg: double, float, decimal, etc...

Then to use:

VB

dgvProduktion.Rows.Add(..., FormatData(dreader("AZmin")) ,...)